Sithera Wellspun is one of seven ghosts that can be found wandering Darkmoon Island while players are in spirit form after dying. She can be found on the lower eastern portion[62, 66] of the island, walking in a mostly north-south route. Speaking to her reveals the following, though it requires multiple interactions:

I was supposed to get firewood for the campsite...

I have such a hard time gathering firewood...

I thought I saw something in the bushes nearby... Then I guess I blacked out.

When I woke up, I couldn't find my way back to the campsite...

It appears Sithera may have died from exposure after becoming lost; either that, or her "waking up" was when she gained awareness as a ghost after dying. In this case, she would have died of fright.